A chromium catalyst, its preparation and use

ABSTRACT

Disclosed herein is a chromium oxide catalyst composition having reduced levels of chromium (VI), methods of making a chromium oxide catalyst composition and system, and illustrative uses of the chromium oxide catalyst composition and system. The catalyst disclosed may be a gel and may comprise chromium (III) oxide and chromium (VI) oxide at an amount of about 10,000 ppm or less based on total chromium oxide contents in the chromium oxide catalyst composition.

TECHNICAL FIELD

The present disclosure relates to a chromium catalyst composition and toa chromium catalyst system with reduced levels of chromium(VI) oxide aswell as to methods for preparing the chromium catalyst composition andsystem and their use.

BACKGROUND

Chromium(VI), also known as hexavalent chromium and Cr(VI), is a toxicform of the element chromium. Hexavalent chromium has many differentindustrial applications acting a precursor or as an intermediate. Someof its uses include chromate pigments in dyes, paints, inks and plastic;chromium catalysts; an anti-corrosive chromium agent added to paints,primers, and other surface coatings; chrome electroplating; welding andhotworking chrome alloys and chrome coated metals. It may also bepresent as an impurity in portland cement. Exposure to high levels ofhexavalent chromium could have short and long term health consequencesto employees in these industries. Short term consequences could affectthe nose, throat, lungs, and skin. Some of the symptoms includeirritation to the nose and throat, runny nose, sneezing, coughing,itching, burning sensation, wheezing, shortness of breath, swelling, ared itchy rash, and a chrome ulcer upon direct skin contact withhexavalent chrome. The long term consequences include irritation anddamage to the respiratory tract, eyes, and skin and in some instanceseven lung cancer. In fact, regulatory agencies consider all Cr(VI)compounds to be occupational carcinogens.

Commercially available chromium(III) oxide catalysts (Cr₂O₃) aresynthesized by a plurality of routes including 1) a sol-gel processwhere suitable precursors such chromic acid or chromium(VI) oxide (CrO₃)are reduced with organic chemicals and 2) a precipitation process wherechromium hydroxide is precipitated and treated to form chromium(III)oxide and 3) a thermal process where suitable chromium precursorcompounds are thermally converted to form chromium(III) oxide andvolatile by-products. Experimental results illustrate that the catalystsresulting from currently available routes have a rather high Cr(VI)content that does not meet the latest toxic and hazardous substancesregulations. This shortcoming may render their production, handling,operation and disposal impractical in particular on industrial scale.

Cr(VI) reduction has been the focus in the last few decades in areas ofenvironmental remediation of Cr(VI) pollution in water and soil andCr(VI) exposure to employees. While methods that combine reducingagents, chelating agents, and organic chemicals have contributedsignificantly to environmental clean-up and wastewater treatment ofCr(VI), these methods have not been found applicable for industrialscale production of Cr₂O₃ material for catalyst applications with lowCr(VI) levels.

There is a need in the art for chromium catalysts with minimal Cr(VI)levels and to identify an industrially applicable process for producingCr₂O₃ material for chromium catalyst applications.

SUMMARY

Disclosed herein are chromium oxide catalyst compositions and chromiumoxide catalyst systems with minimal Cr(VI) oxide content, processes oftheir preparation, methods of their use, and their various applications.

In some embodiments, the invention is directed to a process forpreparing a chromium oxide catalyst composition, the process comprising:forming a mixture comprising chromium(VI) oxide in an aqueous solventand in an organic reducing solvent; refluxing the mixture to form aslurry; and drying the slurry to form a powder having chromium(VI) oxideat an amount of about 10,000 ppm or less based on total chromium oxidescontent in the dried powder. In some embodiments, the dried powder maybe calcined. In some embodiments, the dried powder or the dried calcinedpowder may further be blended with a lubricant, such as graphite. Insome embodiments, the dried powder or the dried calcined powder, whetheror not blended with a lubricant, may be compressed into various shapes(e. g. to form tablets), pelletized, or processed by extrusiontechniques (e. g. to form extrudates)

In some embodiments, a mixture of chromium(VI) in an aqueous solvent andin an organic reducing solvent may be formed by first dissolvingchromium(VI) oxide in an aqueous solvent to form a solution (designatedas “solution A”) and thereafter adding the organic reducing solvent tosolution A to form a slurry. In other embodiments, the mixture may beformed by first dissolving chromium(VI) oxide in an aqueous solvent toform solution A and thereafter adding solution A into the organicreducing solvent. In yet other embodiments, the mixture may be formed byfirst mixing the aqueous solvent with the organic reducing solvent andthereafter adding chromium(VI) oxide into the mixture.

In some embodiments, the dried powder, dried calcined powder, blendedpowder, compressed powder, pelletized powder, extruded powder and/or allother solid intermediates in the process may have chromium(VI) oxide atan amount of about 10,000 ppm or less, about 5,000 ppm or less, about2,000 ppm or less, about 1,000 ppm or less, about 500 ppm or less, about250 ppm or less, or about 100 ppm or less based on total chromium oxidescontent in the solid intermediate.

In some embodiments, the invention is directed to a process forpreparing a chromium oxide catalyst composition, the process comprisesreducing the chromium(VI) to a chromium(III). In some embodiments, theprocess comprises oxidizing the organic reducing solvent. In someembodiments, the molar ratio of the organic reducing solvent to thechromium(VI) oxide may range from about 0.2 to about 4.0, from about 0.3to about 3.0, from about 0.4 to about 2.0, from 0.5 to about 1.5, fromabout 0.6 to about 1.3, from about 0.75 to about 1.5, or from about 1 toabout 1.25.

In one embodiment, the aqueous solvent may comprise water. In someembodiments, the organic reducing solvent may comprise an alcohol, analdehyde, a carboxylic acid, or combinations thereof. In one embodiment,the alcohol may comprise isobutyl alcohol. In an embodiment, the organicreducing solvent may comprise benzyl alcohol. In an embodiment, theorganic reducing solvent may comprise a combination of ethanol andisobutyric acid or a combination of ethanol and acetic acid. The mixtureof aqueous solvent and organic reducing solvent may form a binary phasemixture or a ternary phase mixture. In some embodiments, the organicreducing solvent acts as a solvent and as a reducing agent. In someembodiments, no additional reducing agents, solvents, or chelatingagents are added to the process.

In one embodiment, when the aqueous solvent comprises water and theorganic reducing solvent comprises isobutyl alcohol, the process maycomprise: dissolving chromium(VI) oxide in water; oxidizing the isobutylalcohol to form isobutyraldehyde and isobutyric acid; and reacting theisobutyric acid with the dissolved chromium(VI) oxide to form acetoneand carbon dioxide.

In some embodiments, the invention is directed to a process forpreparing a chromium oxide catalyst composition, wherein the catalystcomposition may be an amorphous gel. In some embodiments, the amorphousgel may be about 80% or more, about 85% or more, about 90% or more,about 95% or more, about 98% or more, about 99% or more, or about 100%amorphous. In some embodiments, the amorphous gel may be a xerogel.

In some embodiments, the invention is directed to a catalyst compositionprepared by a reduction route. In other embodiments, the invention isdirected to a catalyst composition prepared by a precipitation route. Inyet other embodiments, the invention is directed to a catalystcomposition prepared by a thermal decomposition route. The reduction,the precipitation and the thermal decomposition routes will be discussedin further detail below. In some embodiments, the invention may bedirected to a chromium oxide catalyst composition prepared by otherroutes which would yield a chromium oxide catalyst composition asdisclosed herein.

In some embodiments, the invention is directed to a chromium oxidecatalyst composition comprising: a chromium(III) oxide and achromium(VI) oxide, wherein the chromium(VI) oxide may be present at anamount of about 10,000 ppm or less, about 5,000 ppm or less, about 2,000ppm or less, about 1,000 ppm or less, about 500 ppm or less, about 250ppm or less, or about 100 ppm or less based on total chromium oxides inthe catalyst composition. In some embodiments the chromium(III) oxidemay be present in an amount of about 99 wt % or more, based on totalchromium oxides in the catalyst composition.

In some embodiments, the chromium(III) oxide and the chromium(VI) oxide,in total, are present at an amount of about 80 wt % or more, about 85 wt% or more, about 90 wt % or more, about 95 wt % or more, about 96 wt %or more, about 97 wt % or more, about 98 wt % or more, or about 99 wt %or more based on total weight of the chromium oxide catalystcomposition.

In some embodiments the chromium oxide catalyst composition may have aBET (Brunauer-Emmett-Teller) surface area of about 50 m²/g or more, orof about 150 m²/g or more. The BET surface area may be measured andcalculated according to the BET model disclosed in ISO 9277:2010(described in further detail below). In some embodiments, the BETsurface area may range from about 150 m²/g to about 350 m²/g, from about200 m²/g to about 325 m²/g, or from about 300 m²/g. In some embodimentsthe chromium oxide catalyst composition may have a high pore volume. Insome embodiments the chromium oxide catalyst composition may becompressed into various shapes (e. g. to form tablets), pelletized, orprocessed by extrusion techniques (e. g. to form extrudates).

In some embodiments the invention is directed to a chromium oxidecatalyst system comprising a chromium oxide catalyst composition incontact with a substrate. In some embodiments, the catalyst compositionand/or the catalyst system may further comprise one or more promotersand/or co-catalysts.

In some embodiments the invention is directed to a method of making ahydrohalocarbon compound, the method comprising: contacting ahydrohalocarbon starting materials with a chromium oxide catalystcomposition and/or with a chromium oxide catalyst system according to anembodiment disclosed herein.

The term “substrate” refers to a material (e.g. a metal, semi-metal,semi-metal oxide or metal oxide) onto or into which the catalystcomposition is placed. In some embodiments, the substrate may be in theform of a solid surface having a washcoat containing a plurality ofcatalytic particles. In some embodiments, the substrate may be in a formof a porous solid surface and the catalyst composition may beimpregnated thereon outside the pores and/or inside the pores. Suitablesubstrate geometries comprise extrudates, spheres, tablets, monoliths,honeycombs, pellets, granulates and powders.

The term “amorphous” refers to the presence of a baseline backgroundsignal and the absence of sharp reflections in the diffractogram when asample is analyzed under x-ray diffraction (XRD)

The term “xerogel” refers to a gel prepared by the sol-gel process anddried under normal conditions, e.g, by evaporation. The normal dryingconditions may exert capillary pressure on the gel, thereby shrinking aswell as densifying the gel network to form a xerogel.

The terms “chromium(VI) oxide” and “chromic acid” are usedinterchangeably throughout the application and are also understood toencompass other common names such as “chromium trioxide” and “chromicanhydride”.

The term “total chromium oxides content” refers to the sum of allchromium oxide species present and is meant to encompass variousoxidation states, including but not limited to, chromium(III) oxide,chromium(VI) oxide, chromium (IV) oxide, and chromium (II) oxide.

The term “catalyst composition” refers to the active component(s)responsible for the catalytic activity.

The term “catalyst system” refers to the catalyst composition as well asany supplemental additive(s) such as substrates, promoters, binders,stabilizers, and so on.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure, their nature,and various advantages will become more apparent upon consideration ofthe following detailed description, taken in conjunction with theaccompanying drawing, in which:

FIG. 1 depicts a schematic of the process for preparing a chromium oxidecatalyst composition according to an embodiment.

DETAILED DESCRIPTION

The present disclosure relates to a process for making a chromium oxidecatalyst composition with minimal chromium(VI) content. The processesdisclosed herein have many advantages, such as: using an organicreducing solvent having a single organic chemical (or in someembodiments two organic chemicals) without additional chemicals orchelating agents; using a sol-gel process; all intermediates encounteredat different steps in the processes have minimal chromium(VI) oxidelevels thus enabling safe industrial-scale handling, and in someembodiments have chromium(VI) oxide levels that are below the regulatedlimit.

A Method for Preparing a Chromium Oxide Catalyst Composition and/orSystem

The present disclosure relates to methods for preparing a chromium oxidecatalyst composition and/or system having minimal chromium(VI) oxidelevels, and in some embodiments, methods for preparing a chromium oxidecatalyst composition and/or system having chromium(VI) oxide levels thatare below the regulated limits.

In some embodiments, porous Cr₂O₃ powder with reduced levels ofchromium(VI) oxide may be prepared by a process known as the “reductionroute” or as the “organic route.” This process utilizes ethanol and/orother reducing agents to reduce the chromium(VI) oxide to chromium(III)oxide. Illustrative reduction route processes have been discussed inU.S. Pat. No. 2,271,356 (disclosing a gel type Cr₂O₃ catalyst preparedby reacting chromium(VI) oxide with various reducing agents (e.g.,ethanol and oxalic acid) in aqueous solution) and U.S. Pat. No.3,258,500 (disclosing a sol-gel process and a pigment drying process forthe preparation of a Cr₂O₃ catalyst). The processes disclosed in thesepatents may be further modified, as disclosed herein, to produce a finalchromium oxide catalyst composition and/or system having reduced levelsof chromium(VI) oxide.

In some embodiments, a catalyst composition may be prepared using a“precipitation route,” also known as an “inorganic route.” This processutilizes chromium(III) salt precursors (such as nitrate salts, chloridesalts, sulfate salts, etc) dissolved in an aqueous solution and treatedwith a solution, such as ammonia solution, to form a chromium hydroxideprecipitate. Under the inorganic route, the chromium hydroxideprecipitate may undergo additional treatment steps, such as filtration,drying, calcination and so on to form chromium oxide. Illustrativeprecipitation route processes for the preparation of chromium oxide havebeen discussed in U.S. Pat. Nos. 6,300,531, 5,523,500, and 5,155,082(disclosing an exemplary process of aqueous chromium salt being mixedwith aqueous ammonia or alkali metal hydroxide to precipitate chromiumhydroxide).

In some embodiments, a catalyst composition may be prepared using a“thermal decomposition” route. This process utilizes chromium precursors(such as ammonium dichromate(VI), sodium dichromate(VI), potassiumdichromate(VI), chromic acid, etc.) which upon thermal treatment(usually at elevated temperatures above 400° C.) will form chromiumoxide and will release volatile by-products. Depending on the choice ofthe chromium precursors, the chromium oxide obtained by the “thermaldecomposition” route may contain or may not contain e g ammonium, sodiumor potassium. The level of such compounds may be reduced by a washingstep with water or a suitable organic solvent after the thermaldecomposition of the chromium precursor has been carried out.Illustrative processes for the preparation of chromium oxide followingthe “thermal decomposition” route have been discussed in U.S. Pat. No.5,036,036.

The processes disclosed in these patents may be further modified, asdisclosed herein, to produce a final catalyst composition and/or systemhaving reduced levels of chromium(VI) oxide. It is an object of thepresent invention to encompass chromium(III) oxide catalyst compositionsand/or systems prepared by all of the routes disclosed herein.

The various embodiments are now described with reference to thefollowing FIGURES and examples. Before describing several exemplaryembodiments, it is to be understood that the present disclosure is notlimited to the details of construction or process steps set forth in thefollowing description. Other embodiments may be practiced or carried outin various ways in accordance with the principles described.

FIG. 1 depicts a schematic illustrating an exemplary sol-gel process 100for preparing a chromium oxide catalyst composition according to anembodiment of the invention. At block 110, the process may comprise:forming a mixture comprising chromium(VI) oxide, an aqueous solvent, andan organic reducing solvent. The mixture may be formed in anyconceivable order. In some embodiments, the chromium(VI) oxide may bedissolved in the aqueous solvent to form a solution A first, andthereafter the organic reducing solvent may be added to solution A. Insome embodiments, solution A may be added to the organic reducingsolvent. In some embodiments, the aqueous solvent and the organicreducing solvents may be mixed or premixed and the chromium(VI) oxidemay be added to the mixture of solvents. The addition may be controlledover a predetermined period of time. Alternatively, the addition may beinstantaneous.

In some embodiments, the aqueous solvent may be water. In someembodiments, the organic reducing solvent may be an alcohol, analdehyde, a carboxylic acid, or a combination thereof, for example,methanol, ethanol, propanol, isopropanol, butanol, isobutanol,n-butanol, sec-butanol, tert-butanol, isoprenol, benzyl alcohol,isobutyraldehyde, isobutyric acid, acetic acid, ethanol and acetic acid,ethanol and isobutyric acid, etc. In some embodiments, the aqueoussolvent and organic reducing solvent may form a binary phase mixture ora ternary phase mixture depending on the solubility of the solvents inone another. In some embodiments, the addition may lead to an exothermicreaction and increase the temperature of the mixture.

In some embodiments, the molar ratio of the organic reducing solvent tothe chromium(VI) oxide may range from about 0.2 to about 4.0, from about0.3 to about 3.0, from about 0.4 to about 2.0, from about 0.5 to about1.5, from about 0.6 to about 1.3, from about 0.75 to about 1.5, or fromabout 1 to about 1.25.

At block 120, the process may further comprise: refluxing the mixture toform a slurry. The refluxing may occur at an elevated temperatureranging from about 50° C. to about 250° C., from about 70° C. to about150° C., or from about 85° C. to about 95° C. The refluxing may takeplace over a time period ranging from about 30 minutes to about 24hours, from about 1 hour to about 20 hours, from about 3 hours to about16 hours, or for the duration of time necessary to reduce thechromium(VI) oxide content in the resulting slurry below a predeterminedlevel. The predetermined level may be for example about 10,000 ppm orless, about 5,000 ppm or less, about 2,000 ppm or less, about 1,000 ppmor less, about 500 ppm or less, about 250 ppm or less, or about 100 ppmor less of chromium(VI) oxide based on the total chromium oxides contentpresent in the slurry.

The existence of refluxing, its temperature, and duration may bedependent on the aqueous and organic reducing solvent used in theprocess. In some embodiments, there may be no refluxing whatsoever. Insome embodiments, a first reducing organic solvent mixed with solution Amay be refluxed for a first duration. The first duration may range fromabout 30 minutes to about 24 hours, from about 1 hour to about 20 hours,from about 3 hours to about 16 hours, or for the duration of timenecessary to reduce the chromium(VI) oxide content in the resultingslurry below a predetermined level. Thereafter, a second reducingorganic solvent may be added and subsequently the mixture and/or slurrymay be further refluxed for a second duration after the addition of thesecond reducing organic solvent to reach a desired chromium(VI) oxidelevel. The second reflux duration and temperature may be equal to,shorter, or longer than the first reflux duration and temperature andmay be dependent on the aqueous and organic chemical(s) used in theprocess.

At block 130 the process may further comprise: reducing the chromium(VI)in the mixture to chromium(III). In some embodiments, the reductionreaction occurs immediately upon formation of the aqueous solvent,organic reducing solvent, and chromium(VI) oxide mixture. In someembodiments, the reduction reaction occurs during refluxing. Thereduction may occur during a single refluxing step or during multiplerefluxing steps. In some embodiments, the organic reducing solvent actsas both a reducing agent and as a solvent and reduces the chromium(VI)into chromium(III). In some embodiments, the organic reducing solventgets oxidizes as a consequence of reducing the chromium(VI) intochromium(III). In some embodiments, the mixture and/or the slurry arefree of any other additives such as reducing agents or chelating agentsand the only components in the mixture and/or slurry are the aqueoussolvent, the organic reducing solvent, the chromium(VI) oxide, and anyreaction products arising therefrom.

In one embodiment, the aqueous solvent may comprise water and theorganic reducing solvent may comprise isobutyl alcohol. The chromium(VI)oxide may be dissolved in water to form a chromium(VI) oxide solution.The isobutyl alcohol may then be added to the chromium(VI) oxidesolution to form a binary mixture. The addition of isobutyl alcohol mayresult in an exothermic reaction, thereby increasing the temperature ofthe mixture to a range of, e.g., from about 25° C. to about 50° C.External heating may be used to increase the temperature of the mixtureto a range of, e.g., from about 85° C. to about 95° C. The temperaturemay be maintained at the temperature range obtained with externalheating and the reaction may then be refluxed for about 3 hours. Duringthe refluxing, several reactions may occur, for example: 1) chromium(VI)may be reduced to chromium(III); 2) isobutyl alcohol may be oxidized toisobutyraldehyde and isobutyric acid; and 3) isobutyric acid may reactwith the chromium(VI) oxide to form acetone and carbon dioxide. At block130 a sol-gel slurry may be formed. These reactions, as well asreactions occurring in other embodiments, may achieve a chromium(VI)oxide level that is about 10,000 ppm or less, about 5,000 ppm or less,about 2,000 ppm or less, about 1,000 ppm or less, about 500 ppm or less,about 250 ppm or less, or about 100 ppm or less based on the totalchromium oxides content present in the slurry.

The sol-gel slurry may then proceed to block 140, drying the slurry toform a powder having minimal levels of chromium(VI) oxide. When thesol-gel slurry is dried under normal conditions, i.e., where the liquidis evaporated gradually and not at supercritical conditions, a densexerogel may be formed. The drying may occur at a temperature rangingfrom about 50° C. to about 200° C., from about 100° C. to about 150° C.,or at about 120° C. In some embodiments, the drying may be performed inair. In other embodiments, the drying may be performed under nitrogen.In some embodiments, drying the slurry may form a cake, and the cake maythereafter be granulated to form a dried powder.

The dried powder may optionally be calcined as depicted in block 150.The calcining may occur at a temperature ranging from about 300° C. toabout 500° C. or from about 350° C. to about 450° C. In someembodiments, the calcining may be performed in air. In otherembodiments, the calcining may be performed under nitrogen. In yet otherembodiments the calcination may be performed under steam.

The dried powder, whether calcined or not, may optionally be blendedwith a lubricant as depicted in block 160. The lubricant may improve theflowability of the resulting catalyst composition. The lubricant may beone or more of graphite, polytetrafluoroethylene (PTFE) or hexagonalboron nitride, molybdenum disulfide, tungsten disulfide, chromiumacetate hydrate, or chromium acetate hydroxide. In some embodiments, thelubricant may be graphite with a low percentage of water.

The dried powder, whether calcined or not and whether blended with alubricant or not, may optionally be compressed into various shapes(e.g., to form tablets), pelletized, or processed by extrusiontechniques (e.g., to form extrudates) as depicted in block 170. Forexample, the compressed, pelletized, or extruded catalyst compositionmay be shaped as pellets, beads, extrudates, rings, spheres, cylinders,trilobe, and quadralobe shaped pieces.

The dried powder (regardless of whether calcined, blended with alubricant, compressed or pelletized) may form a final chromium oxidecatalyst composition, pursuant to block 180, described in furtherdetails below.

The chromium(VI) oxide level in the dried and/or calcined and/or blendedand/or compressed and/or pelletized powder and/or extruded and/or finalchromium oxide catalyst composition may be about 10,000 ppm or less,about 5,000 ppm or less, about 2,000 ppm or less, about 1,000 ppm orless, about 500 ppm or less, about 250 ppm or less, or about 100 ppm orless based on the total chromium oxides content present in the driedand/or calcined and/or blended and/or compressed and/or pelletizedpowder and/or extruded and/or final chromium oxide catalyst composition.

The concentration of dissolved chromium(VI) or chromium(VI) oxide may bemeasured in accordance with publicly available EPA's (EnvironmentalProtection Agency) method 7196A. In method 7196A the concentration ofdissolved chromium(VI) is determined colorimetrically by reacting thechromium(VI) with diphenylcarbazide in acid solution. A red-violet colorof unknown composition is produced in the reaction. The composition'sabsorbance may be measured photometrically at 540 nm. Since the reactioncould be sensitive, precautions are taken to ensure that the reactionoccurs in the absence of interfering amounts of substances such asmolybdenum, vanadium, mercury, and iron, which could also react withdiphenylcarbazide to form color. Exemplary colorimetric equipment thatmay be used include: a spectrophotometer, for use at 540 nm, providing alight path of 1 cm or longer; or a filter photometer, providing a lightpath of 1 cm or longer and equipped with a greenish-yellow filter havingmaximum transmittance near 540 nm.

The final chromium oxide catalyst composition may also be combined withsupplemental additive(s) to form a final chromium oxide catalyst system.For example, the chromium oxide catalyst composition may be disposedonto and/or into a substrate, or the chromium oxide catalyst compositionmay be combined with one or more of a promoter, binder, co-catalyst, orcombinations thereof at various stages of the process.

Chromium Oxide Catalyst Composition

In some embodiments, the invention is directed to a chromium oxidecatalyst composition comprising: a chromium(III) oxide and achromium(VI) oxide, wherein the chromium(VI) oxide may be present at anamount of about 10,000 ppm or less, about 5,000 ppm or less, about 2,000ppm or less, about 1,000 ppm or less, about 500 ppm or less, about 250ppm or less, or about 100 ppm or less based on total chromium oxides inthe chromium oxide catalyst composition. In some embodiments thechromium(III) oxide may be present in an amount of about 99 wt % ormore, based on total chromium oxides in the chromium oxide catalystcomposition.

In some embodiments, the chromium(III) oxide and the chromium(VI) oxide,in total, are present in the catalyst composition at an amount of about80 wt % or more, about 85 wt % or more, about 90 wt % or more, about 95wt % or more, about 96 wt % or more, about 97 wt % or more, about 98 wt% or more, or about 99 wt % or more based on total weight of thechromium oxide catalyst composition.

In some embodiments, the chromium oxide catalyst composition, may be anamorphous gel, such as xerogel. In some embodiments, the amorphous gelmay be about 80% or more, about 85% or more, about 90% or more, about95% or more, about 98% or more, about 99% or more, or about 100%amorphous. Amorphous contents disclosed herein may be measured using anPANalytical X'Pert Pro XRD instrument. The instrument is calibrated with100% NBS (Nation Bureau of Standards) standard. All samples were scannedbetween two theta angles ranging from about 32.5° to about 34.5°,ensuring that the scan encompassed major peaks of α-Cr₂O₃ (d-2.665)which are typically present at a two theta angle of about 33.6°. Theamorphous content determination is performed using Rietveld analysis.

In some embodiments the chromium oxide catalyst composition may have ahigh BET surface area of about 150 m²/g or more. In some embodiments,the BET surface area of the chromium oxide catalyst composition mayrange from about 150 m²/g to about 350 m²/g, from about 200 m²/g toabout 325 m²/g, from about 240 m²/g to about 325 m²/g, or about 300m²/g. BET surface areas disclosed herein may be measured using twoMicromeritics instruments, namely: Gemini V/VII surface area analyzers,and TriStar II plus. The ISO (International Organization ofStandardization) test method on both instruments is 9277:2010, entitled“determination of the specific area of solids by gas adsorption BETmethod.”

The chromium oxide catalyst composition may have a median bulk densityranging from about 0.3 g/cc to about 1.0 g/cc, from about 0.4 g/cc toabout 0.9 g/cc, or from about 0.45 g/cc to about 0.8 g/cc. Bulkdensities disclosed herein may be measured using the American Societyfor Testing Materials (ASTM) D7481-09 method, entitled “standard testmethod for determining loose and tapped bulk density of powders usinggraduated cycliner,” and is analyzed on a Scott paint volumeter(densitometer) instrument.

The chromium oxide catalyst composition may be porous with pore volumesranging from about 0.2 cc/g to about 2.0 cc/g, from about 0.4 cc/g toabout 1.5 cc/g, or from about 0.4 cc/g to about 1.2 cc/g. Pore volumesdisclosed herein may be measured by two methods, namely, the mercury(Hg) method and the nitrogen (N₂) method. The Hg method utilizes theASTM D4284-12 method, entitled “standard test method for determiningpore volume distribution of catalyst and catalyst carriers by mercuryintrusion porosimetry,” and is analyzed on a Micromeritics AutoPore Vinstrument. The N₂ method utilizes the ASTM D4222-03(2008) method,entitled “standard test method for determining of nitrogen adsorptionand desorption isotherms of catalyst and catalyst carriers by staticvolumetric measurements,” and is analyzed on a Micromeritics TriStar IIPlus instrument.

In some embodiments the chromium oxide catalyst composition may comprisevarious shapes, such as tablets, pellets, beads, extrudates, rings,spheres, cylinders, stars, hollow stars, trilobe, hollow trilobe, aquadralobe and hollow quadrolobe shaped pieces.

Chromium Oxide Catalyst System

In some embodiments the invention is directed to a chromium oxidecatalyst system comprising a chromium oxide catalyst composition incontact with a substrate, such as alumina (Al₂O₃), aluminum fluoride(AlF₃), fluorinated alumina, silica (SiO₂), zirconia (ZrO₂), titania(TiO2), magnesium oxide (MgO), magnesium fluoride (MgF₂), calciumfluoride (CaF₂), carbon materials (such as activated carbon, charcoal,or carbon black), or combinations thereof. The substrate may be presentin the chromium oxide catalyst system in an amount of up to about 95 wt% based on the total weight of the chromium oxide catalyst system.

In some embodiments, the chromium oxide catalyst system may furthercomprise one or more co-catalysts and/or promoters, for example lithium(Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium(Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba),scandium (Sc), yttrium (Y), zirconium (Zr), hafnium (HD, vanadium (V),niobium (Nb), tantalum (Ta), tungsten (W), manganese (Mn), rhenium (Re),iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh),iridium (Ir), zinc (Zn), nickel (Ni), palladium (Pd), platinum (Pt),copper (Cu), silver (Ag), gold (Au), cadmium (Cd), mercury (Hg), boron(B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon(Si), phosphorus (P), arsenic (As), bismuth (Bi), selenium (Se),tellurtum (Te), thorium (Th), uranium (U), titanium (Ti), molybdenum(Mo), lead (Pb), tin (Sn), germanium (Ge), antimony (Sb), a compoundbased on an element from the lanthanide series (rare earth elements), orcombinations thereof.

Suitable compounds of co-catalysts and/or promoters comprise halides,oxides, oxyhalides, or mixtures thereof. Promoters and/or co-catalystsmay also be present in their elemental state, e.g., in their metallic orsemi-metallic form. The co-catalyst and/or promoters may be part of thechromium oxide catalyst composition and may be in contact with thesubstrate. Processes known in the art, such as impregnation,co-precipitation, or powder mixing may be applied to include promotersand/or co-catalysts in the catalyst system. The chromium oxide catalystsystem preparation may be assisted by the addition of a process solventsuch as e. g. water, organic solvents, dilute acids (e. g. nitric acid),dilute bases (e. g. ammonia) or mixtures thereof. The promoters and/orco-catalysts may be present in the chromium oxide catalyst system in anamount ranging from about 0.5 wt % to about 30 wt % based on the totalweight of the chromium oxide catalyst system.

Method of Making Hydrohalocarbons

Historically, ammonia was used in refrigeration. Its high toxicity andfatal consequences resulting from ammonia leaks led to the developmentof chlorofluorocarbons (CFCs) and fluorocarbons (FCs). CFCs aresynthetic compounds, composed of the elements chlorine, fluorine, andcarbon, that have been developed primarily for refrigerant applications.These compounds were deemed particularly suitable as refrigerants due totheir inert, nontoxic, and easily compressible nature. FCs are syntheticcompounds, composed of the elements fluorine and carbon only.

It was later discovered that CFCs are harmful to the environment. OnceCFCs are released into the air, they slowly drift upward in theatmosphere and remain unreacted for long periods of times until theyreach the stratosphere where they get exposed to ultraviolet light fromthe sun, which in turn activates the CFCs and breaks theircarbon-chloride bond, thereby releasing chlorine atoms. The chlorineatoms react with the ozone in the stratosphere, which hinders theozone-oxygen equilibrium in the stratosphere and contributes to thedestruction of the stratospheric (high altitude) ozone, also known as“ozone layer.”

As a result, future production and use of CFCs were greatly limited andin some instances banned. CFC production has been totally phased out bythe end of the twentieth century. Hydroflurocarbons (HFCs) andhydrochlorofluorocarbons (HCFCs), also known as third generationhalocarbons, were introduced as a CFC replacement in the refrigerationindustry. HFCs are composed of hydrogen and fluorine bound to carbonatoms and HCFCs are composed of hydrogen, fluorine, and chlorine atomsbound to carbon atoms. The presence of hydrogen-carbon bonds makes HFCsand HCFCs more reactive than CFCs and thus more susceptible toenvironmental degradation. Thus, HFCs and HCFCs get destroyed at loweraltitudes without reaching and harming the stratosphere. At the sametime, the presence of a hydrogen atom reduced the boiling point of HFCsand HCFCs, resulting in inferior refrigeration efficiency as compared toHFCs. Additionally, while HFCs and HCFCs do not reach the stratosphere,they have been identified as potent greenhouse gases contributing to theacceleration of global warming as a result of their increasingconcentration in the lower atmosphere.

Therefore, recent efforts to phase out HFCs and HCFCs were undertakenwith the goal to develop a fourth generation of hydrohalocarbons such ashydrofluoroolefins (HFOs), hydrochlorofluoroolefins (HCFOs) andhydrocarbons (HCs). HFOs are unsaturated HFCs, composed of hydrogen andfluorine bound to carbon atoms, but contain at least one double bondbetween the carbon atoms. HCFOs are unsaturated HCFCs, composed ofhydrogen, chlorine and fluorine bound to carbon atoms, but contain atleast one double bond between the carbon atoms. HCs, also referred to as“natural refrigerants” as they are created by nature, are composed ofhydrogen and carbon only. HFOs and HCs are considered environmentallyfriendly due to their low impact on greenhouse gases, minimal globalwarming potential, low ozone depletion potential, cost efficiency, andenergy efficiency. Exemplary HFOs that are being developed on a globalscale for various applications such as e. g. refrigeration (includingmobile and stationary applications, chilling and air-conditioning) andfoam blowing include 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf),trans-1,3,3,3-tetrafluoro-1-propene (HFO-1234ze(E)),cis-1,3,3,3-tetrafluoro-1-propene (HFO-1234ze(Z)),trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)),cis-1-chloro-3,3,3-trifluoropropene (HCFO-1233 zd(Z)),3,3,3-trifluoropropene (HFO-1243 zf),1-chloro-2,3,3,3-tetrafluoropropene (HFO-1224yd) and1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mz) and their constitutional(structural) isomers and stereoisomers (spatial isomers). All thesecompounds have a negligible ozone depletion potential and extremely lowglobal warming potentials. HFO-1234yf has been used in vehicles (inEurope in 2011 model-year cars and in the United States in 2013model-year cars). HFO-1234ze(E) is intended to be used in e.g.,residential, light commercial air conditioning and heat pumpapplications, vending machines, fridges, beverage dispensers, airdryers, carbon dioxide cascade systems in commercial refrigeration, andso on.

HCs are currently being used in Europe as stand-alone refrigerantsapplications such as refrigerators, bottle coolers, split airconditioning units, domestic refrigerators, freezers, and so on. In theUnited States, the use of HCs is somewhat more limited due to their highflammability.

In general, also blend systems containing two or more hydrohalocarbonsselected from the group of CFCs, FCs, HCFCs, HFOs, HCFOs and HCs may beapplied to the applications mentioned above. In such blends,hydrohalocarbons may be selected from the same or from different of theabove groups. For example, R404A is a commercial blend containingHFC-125, HFC-143a and HFC-134a in a ratio of 44%/52%/4%, R407C is acommercial blend containing HFC-32, HFC-125 and HFC-134a in a ratio of23%/25%/52% and R410A is a commercial blend containing HFC-32 andHFC-125 in a ratio of 50%/50%.

In some embodiments the invention is directed to a method of making ahydrohalocarbon comprising: contacting a hydrohalocarbon startingmaterials with a chromium oxide catalyst composition or a chromium oxidecatalyst system according to an embodiment. Such method may be carriedout using a fixed-bed, moving-bed, fluidized-bed or slurry-bed reactordesign applying gas-phase, vapor-phase, liquid-phase, slurry phase ormixed gas/liquid reactor operation conditions. Such method may becarried out in a continuous manner or in a batch-type manner There aremany known methods to introduce fluorine into organic compounds, buthydrogen fluoride (HF) is considered to be the most economical source offluorine for many commercial applications. Halogen exchange reactions(e. g. exchanging chlorine atom(s) for fluorine atom(s)), hydrogenreplacement reactions (e. g. exchanging hydrogen atom(s) for fluorineatom(s)) and the addition of hydrogen fluoride (hydrofluorination) tonon-saturated carbon-carbon bonds (including double-bonds andtriple-bonds) are the most frequently employed methods. Suitable methodsare further described in Kirk-Othmer Encyclopedia of ChemicalTechnology, Volume 11, pages 858 to 876, Organic Fluorine Compounds(Author William X. Bajzer) which is herein incorporated by reference.

In some embodiments, suitable methods of making such hydrohalocarboncompounds comprise hydrofluorination reactions in the presence ofhydrogen fluoride (HF). In general such methods also comprisedehydrofluorination reactions in which hydrogen fluoride (HF) isreleased and non-saturated carbon-carbon bonds are formed.

Hydrohalocarbon compounds prepared by the method are for example usefulas refrigerants (including mobile and stationary applications forrefrigeration, chilling and air-conditioning), foam blowing agents,aerosol propellants, solvents, electronic gases, fire extinguishingagents as well as fluoropolymer, fluoroelastomer, chlorofluoropolymerand chlorofluoroelastomer precursors.

The chromium oxide catalyst composition or chromium oxide catalystsystem may also be present in its activated (or regenerated) form priorto its contact with hydrohalocarbon starting materials. Duringactivation (or regeneration) the chromium oxide may be fully orpartially converted to a corresponding chromium oxyhalide, a chromiumhalide, or mixtures thereof. When the chromium oxide catalystcomposition is present as a chromium oxyhalide corresponding to thegeneral empirical formula Cr_(x)O_(y)Hal_(z), where x is 1-2 and y and zare selected such that the valency of chromium (Cr) is satisfied. Thevalency of chromium is typically 3-6. Possible halides (Hal) arechlorides and fluorides. Thus, illustrative activated (or regenerated)forms of chromium may include one or more of oxychlorides, chlorides,chlorofluorides, oxychlorofluorides, oxyfluorides or fluorides ofchromium. Activation (or regeneration) can be for example performed bytreating the chromium oxide catalyst composition with anhydrous hydrogenfluoride (HF), optionally in the presence of oxygen.

Chromium oxide catalyst compositions or catalyst systems for which theactivity has fallen as a consequence of contamination may also beregenerated by cleaning the catalyst composition's or system's surfacewith a compound capable of oxidizing and converting the products(organic products, coke, and the like) deposited on the surface intovolatile products. In this case, oxygen or a mixture containing oxygen(e. g. air) is suitable and enables the catalyst activity to berestored.

In some embodiments, the hydrohalocarbon prepared by methods disclosedherein may include one or more of trichlorofluoromethane (CFC-11),dichlorodifluoromethane (CFC-12), chlorotrifluoromethane (CFC-13),tetrafluoromethane (FC-14), dichlorofluoromethane (HCFC-21),chlorodifluoromethane (HCFC-22), trifluoromethane (HFC-23),chlorofluoromethane (HCFC-31), difluoromethane (HFC-32), perfluorohexane(FC-51-14), pentachlorofluoroethane (CFC-111),1,1,2,2-tetrachloro-1,2-difluoroethane (CFC-112), 1,1,1,2-tetrachloro-2, 2-difluoroethane (CFC-112a),1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113), 1, 1,1-trichloro-2,2,2-trifluoroethane (CFC-113a) 1,2-dichlorotetrafluoroethane (CFC-114), 1,1-dichlorotetrafluoroethane (CFC-114a), chloropentafluoroethane(CFC-115), hexafluoroethane (FC-116), 1,1,2,2-tetrachloro-1-fluoroethane(HCFC-121), 1,1,1,2-tetrachloro-2-fluoroethane (HCFC-121a),1,1,2-trichloro-2,2-difluoroethane (HCFC-122), 1, 1, 2-trichloro-1,2-difluoroethane (HCFC-122a), 1,1,1-trichloro-2,2-difluoroethane(HCFC-122b), 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123),1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a),1,1-dichloro-1,2,2-trifluoroethane (HCFC-123b),2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124),1-chloro-1,1,2,2-tetrafluoroethane (HCFC-124a), pentafluoroethane(HFC-125), 1,1,2-trichloro-2-fluoroethane (HCFC-131), 1,1,2-trichloro-1-fluoroethane (HCFC-131a), 1,1,1-trichloro-2-fluoroethane(HCFC-131b), dichlorodifluoroethane (HCFC-132),1,1-dichloro-2,2-difluoroethane (HCFC-132a), 1,2-dichloro-1,1-difluoroethane (HCFC-132b), 1,1-dichloro-1,2-difluoroethane(HCFC-132c), 2-chloro-1,1,1-trifluoroethane (HCFC-133),2-chloro-1,1,1-trifluoroethane (HCFC-133a), 1-chloro-1, 1,2-trifluoroethane (HCFC-133b), 1, 1,2, 2-tetrafluoroethane (HFC-134),1,1,1,2-tetrafluoroethane (HFC-134a), 1,2-dichloro-1-fluoroethane(HCFC-141), 1,1-dichloro-2-fluoroethane (HCFC-141a), 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,2-difluoroethane(HCFC-141a), chlorodifluoroethane (HCFC-142),1-chloro-1,2-difluoroethane (HCFC-142a), 1-chloro-1,1-difluoroethane(HCFC-142b), 1,1,2-trifluoroethane (HFC-143), 1,1,1-trifluoroethane(HFC-143a), chlorofluoroethane (HCFC-151), 1,2-difluoroethane (HFC-152),1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161),1,1,1,2,2,3,3-heptachloro-3-fluoropropane (CFC-211),1,1,1,3,3,3-hexachloro-2,2-difluoropropane (CFC-212),1,1,1,3,3-pentachloro-2,2,3-trifluoropropane (CFC-213),1,1,1,3-tetrachloro-2,2,3,3-tetrafluoropropane (CFC-214),1,2,2-trichloropentafluoropropane (CFC-215 aa),1,1,2-trichloropentafluoropropane (CFC-215bb),1,2-dichloro-1,1,2,3,3,3-hexafluoropropane (CFC-216),1-chloro-1,1,2,2,3,3,3-heptafluoropropane (CFC-217), octafluoropropane(FC-218), hexachlorofluoropropane (HCFC-221), pentachlorodifluoropropane(HCFC-222), tetrachlorotrifluoropropane (HCFC-223),trichlorotetrafluoropropane (HCFC-224),3,3-dichloro-1,1,1,2,2-pentafluoropropane (HCFC-225ca),1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225 cb),1-chloro-1,1,2,2,3,3-hexafluoropropane (HCFC-226),1,1,1,2,3,3,3-heptafluoropropane (HFC-227 ea), pentachlorofluoropropane(HFC-231), tetrachlorodifluoropropane (HCFC-232),trichlorotrifluoropropane (HCFC-233), dichlorotetrafluoropropane(HCFC-234), chloropentafluoropropane (HCFC-235),1,1,1,2,2,3-hexafluoropropane (HFC-236cb), 1,1,1,2,3,3-hexafluoropropane(HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa),tetrachlorofluoropropane (HCFC-241), trichlorodifluoropropane(HCFC-242), dichlorotrifluoropropane (HCFC-243),1,3-dichloro-1,2,2-trifluoropropane (HCFC-243ca),1,1-dichloro-2,2,3-trifluoropropane (HCFC-243cb),1,1-dichloro-1,2,2-trifluoropropane (HCFC-243cc),2,3-dichloro-1,1,1-trifluoropropane (HCFC-243da),1,3-dichloro-1,2,3-trifluoropropane (HCFC-243ea),1,3-dichloro-1,1,2-trifluoropropane (HCFC-243ec),2,3-dichloro-1,1,1-trifluoropropane (HCFC-243db),chlorotetrafluoropropane (HCFC-244), 2-chloro-1,2,3,3-tetrafluoropropane(HCFC-244ba), 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb),3-chloro-1,1,2,2-tetrafluoropropane (HCFC-244ca),1-chloro-1,2,2,3-tetrafluoropropane (HCFC-244cb),1-chloro-1,1,2,2-tetrafluoropropane (HCFC-244cc),2-chloro-1,1,3,3-tetrafluoropropane (HCFC-244da),2-chloro-1,1,1,3-tetrafluoropropane (HCFC-244db),3-chloro-1,1,2,3-tetrafluoropropane (HCFC-244ea),3-chloro-1,1,1,2-tetrafluoropropane (HCFC-244eb),1-chloro-1,1,2,3-tetrafluoropropane (HCFC-244ec),3-chloro-1,1,1,3-tetrafluoropropane (HCFC-244fa), 1-chloro-1,1,3,3-tetrafluoropropane (HCFC-244fb), 1,2,3,3,3-pentafluoropropane(HFC-245ca), 1,1,1,3,3-pentafluoropropane (HFC-245 fa),1,1,1,2,3-pentafluoropropane (HFC-245eb), 1,1,1,2,2-pentafluoropropane(HFC-245 cb), 1,1,2,3,3-pentafluoropropane (HFC-245ea),1,1,1,2,3-pentafluoropropane (HFC-245 eb), 1,1,1,3,3-pentafluoropropane(HFC-245fa), trichlorofluoropropane (HCFC-251), dichlorodifluoropropane(HCFC-252), chlorotrifluoropropane (HCFC-253),2-chloro-1,2,3-trifluoropropane (HCFC-253 ba),2-chloro-1,1,2-trifluoropropane (HCFC-253bb), 1-chloro-2,2,3-trifluoropropane (HCFC-253ca), 1-chloro-1,2,2-trifluoropropane(HCFC-253 cb), 3-chloro-1,1,2-trifluoropropane (HCFC-253 ea),1-chloro-1,2,3-trifluoropropane (HCFC-253 eb),1-chloro-1,1,2-trifluoropropane (HCFC-253 ec),3-chloro-1,3,3-trifluoropropane (HCFC-253 fa),3-chloro-1,1,1-trifluoropropane (HCFC-253 fb),1-chloro-1,1,3-trifluoropropane (HCFC-253fc), 1,1,2,2-tetrafluoropropane(HFC-254cb), dichlorofluoropropane (HCFC-261),1,2-dichloro-2-fluoropropane (HCFC-261ba), chlorodifluoropropane(HCFC-262), 1-chloro-2,2-difluoropropane (HCFC-262ca),3-chloro-1,1-difluoropropane (HCFC-262fa), 1-chloro-1,3-difluoropropane(HCFC-262fb), chlorofluoropropane (HCFC-271), 2-chloro-2-fluoropropane(HCFC-271b), 2-chloro-1-fluoropropane (HCFC-271d),1-chloro-1-fluoropropane (HCFC-271fb), octafluorocyclobutane,1,1,1,4,4,4-hexafluorobutane (HFC-365mfc), decafluoropentane(HFC-4310mee), 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf),trans-1,3,3,3-tetrafluoro-1-propene (HFO-1234ze(E)),cis-1,3,3,3-tetrafluoro-1-propene (HFO-1234ze(Z)),trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233 zd(E)), cis-1-chloro-3,3,3-trifluoropropene (HCFO-1233 zd(Z)),3-chloro-2,3,3-trifluoropropene (HCFO-1233 yf),2-chloro-3,3,3-trifluoropropene (HCFO-1233xf),trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)),cis-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(Z)),3,3,3-trifluoropropene (HFO-1243zf), 1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mz), 1-chloro-2,3,3,3-tetrafluoropropene (HFO-1224yd),1-chloro-1,3,3,3-tetrafluoropropene (HCFO-1224zb),1,1,2-trichloro-3-fluoropropene (HCFO-1231xa),2,3,3-trichloro-3-fluoropropene (HCFO-1231xf),2,3-dichloro-3,3-difluoropropene (HCFO-1232xf),trans-1,2,3,3,3-pentafluoropropene (HFO-1225ye(E)),cis-1,2,3,3,3-pentafluoropropene (HFO-1225ye(Z)),1,1,3,3,3-pentafluoropropene (HFO-1225zc),1,1-dichloro-3,3,3-trifluoropropene (HCFO-1223za),1,1,2-trichloro-3,3,3-trifluoropropene (HCFO-1213xa) and theirconstitutional (structural) isomers and stereoisomers (spatial isomers).

EXAMPLES

The following examples are set forth to assist in understanding theembodiments described herein and should not be construed as specificallylimiting the embodiments described and claimed herein. Such variations,including the substitution of all equivalents now known or laterdeveloped, which would be within the purview of those skilled in theart, and changes in formulation or minor changes in experimental design,are to be considered to fall within the scope of the embodimentsincorporated herein.

Unless specified otherwise, the chromium(VI) oxide contents summarizedin the examples were measured using EPA method 7196A which was describedin further detail hereinbefore. The detection limit for EPA method 7196Ais 0.5 ppm of Cr(VI).

Example 1—Isobutyl Alcohol (IBA) Process

A one liter 4-neck flask equipped with agitator, reflux condenser,coolant chiller and heater, heater controller, temperature probe andrecorder, dropping funnel, distillate receiver with ice bath, andnitrogen purge line, etc. was used for lab experiment runs. Raw materialrecipes were 65 g of CrO₃ and 48 g of IBA (99%). 688 g DI-water wascharged into the flask first, then chromium(VI) oxide was dissolved inwater. Alcohol was pumped into the chromium(VI) oxide solution within 60minutes at a controlled pump rate. The mixture was heated to 85-95° C.and a binary azeotropic phase was formed. Reflux started and held for 16hours. A total of 400 g azeotropic mixture was stripped off at the endof reflux cycle. The slurry was unloaded into a glass tray and driedovernight at 120° C. under air. The dried cake was granulated into apowder form. The dried powder was calcined at about 300° C. to 500° C.for 12 hours under nitrogen.

Effects of organic reducing solvents on chromium(VI) reduction aresummarized in Table 1 below:

TABLE 1 Effects of organic solvents on Cr(VI) Sample 1 Organic SolventIsobutyl Alcohol Organic Solvent/CrO₃ molar ratio 1.0 Driedpowder-Cr(VI) oxide 120 ppm

Table 1 data demonstrates the effectiveness of the isobutyl alcoholprocess at Cr(VI) to Cr(III) oxide reduction.

Example 2—Isobutyl Alcohol Consumption During Reflux

Table below summarizes the isobutyl alcohol concentration changes andconsumption throughout the reflux cycle. The solids and supernatantswere separated by centrifuge at 25° C. Liquid samples were analyzed byGC (Gas Chromatography) and normalized to wt %. The data illustratesthat only about 52% of the initially charged isobutyl alcohol wasconsumed.

TABLE 2 IBA wt % change during reflux cycle Reflux Time Point (Hours)IBA (wt %) IBA cousumption (%) Raw material charge 6.5 0 End of 16 hrsreflux 3.2 51

Example 3—Chromium(VI) Reduction in the Isobutyl Alcohol Process ofExample 1 and 2

Table 3 below illustrates the chromium(VI) oxide level during varioustime points in parts of the reflux cycle.

TABLE 3 Effects of reflux cycle time on Cr(VI) oxide content in theisobutyl alcohol process Reflux Time Point (Hours) Cr(VI) oxide (wt %)Cr(VI) oxide (ppm) 0 100 1,000,000 3 0.417 4,170 6 0.327 3,270

Table 3 illustrates that the rate of chromium(VI) oxide reduction in theIBA process was intensive within the first 3 hours of the refluxingcycle. Reflux cycle extension beyond the first 3 hours continued thechromium(VI) reduction, but at a slower rate.

The chromium(VI) oxide content depicted in Table 3 was obtained using awet chemistry titration method, entitled “an oxidation-reductiontitration method to determine hexavalent chromium content in chromiumproduct and precursor.” The testing procedure included: 1) digesting thesolid sample with nitric acid at a controlled temperature for acontrolled duration; 2) diluting the acid digested solid in a solvent;3) adding a buffer solution comprising a combination of potassiumhydroxide, acetic acid, and potassium iodide; 4) titrating with sodiumthiosulfate; 5) adding a starch indicator solution; and 6) continuing totitrate until the blue color disappears. This titration method has adetection limit of 1000 ppm of Cr(VI).

Example 4—Cr(VI) Reduction with a Single Organic Reducing Solvent

The following reactor set-up and general recipe were used for Examples5-10 below. Specific alterations will be detailed in the correspondingexample.

Reactor System Set-Up

A one liter 4-neck flask equipped with agitator, reflux condenser,coolant chiller, reactor heater, heater controller, temperature probeand recorder, dropping funnel, distillate receiver with ice bath, andnitrogen purge line, etc. was used for lab experiment runs.

Recipe

-   -   1) Charge 688 g of DI-H₂O into reactor;    -   2) Charge X g of chromic acid into reactor, mix for 5-10 minutes        with a fixed rate of agitation for a complete solid dissolution        with a uniform color;    -   3) Pump Y g of organic chemical within 20 to 120 minutes under        constant agitation;    -   4) Heat the mixture inside reactor to a reflux point of a binary        azeotropic phase;    -   5) Keep refluxing within the reactor system for a cycle time of        12-16 hours;    -   6) Strip off 400-415 g of a mixture of organic chemicals and        water;    -   7) Unload the slurry into a dryer for overnight drying at        120-150° C.; and    -   8) Calcine the dried powder under nitrogen at 300-500° C.        overnight.

Example 5—Isopropanol to Chromium(VI) Oxide Optimal Molar RatioDetermination

The reactor set-up and recipe of Example 4 were used herein. X g ofchromic acid (CrO₃) and Y g of isopropanol are depicted in the tablebelow. The chromium(VI) oxide content, surface area, and density valuesillustrated in the table were measured from dried chromium(III) oxidepowder (i.e. powder that was not calcined).

TABLE 4 isopropanol/CrO₃ molar ratio effect on Cr(VI) levels Sample #2#3 X = CrO₃ g 65 60 Y = Isopropanol, g 40 108  Y/X molar ratio   1.0  3.0 Reflux temperature, ° C. 89 84 Cr(VI) oxide, wt %   30.4   23.4(ppm) (304,000)    (234,000)    BET surface area, m²/g 159  216 Density, g/cc    0.48    0.76

A higher Isopropanol/CrO₃ molar ratio improves the Cr(VI) oxidereduction. An increase in molar ratio from 1 to 3, improves the Cr(VI)oxide reduction by about 23%.

Example 6 the Unique Physical Properties of the Resulting Chromium OxideCatalyst

In addition to a low Cr(VI) level, the IBA process of Example 1 alsoproduced a high surface area of both dried and calcined powders. Thiscould be assumed to provide more active surface sites for catalystperformance improvement. Pore volume measured by N₂ and Hg methods showsthat chromium(III) oxide powder obtained in the IBA process is alsodepicted in Table 5. The effects of various organic solvents, e.g.,isopropanol and isobutyl alcohol, on the chromium(VI) oxide content andon the BET surface area of various intermediates, pore volumes ofcalcined powder are summarized in Table 5 below.

TABLE 5 Effects of organic solvents on Cr(VI) oxide levels, BET surfacearea and Pore Volume Isopropanol Isobutyl Alcohol Organic Solvent(Example 5) (Example 1) Dried Powder Cr(VI) oxide (ppm) 304,000 120Surface Area (m²/g) 159 324 Calcined Cr(VI) oxide (ppm) N/A 180 PowderSurface Area (m²/g) N/A 300 N₂ Pore volume (cc/g) N/A 0.46 Hg porevolume (cc/g) N/A 0.99

Example 7—Cr(VI) Oxide Reduction Using C3-C7 Alcohol

The reactor system set-up and recipe of Example 4 were used herein. X gof chromic acid (CrO₃) and Y g of organic chemical (also organicreducing solvent) are depicted in the table below. The chromium(VI)oxide content, surface area and density values illustrated in the tablewere measured from dried chromium(VI) oxide powder (i.e. powder that wasnot calcined).

TABLE 6 Cr(VI) oxide reduction using C2-C7 alcohols Sample #2 #1 #4 #5Alcohol Isopropanol Isobutyl alcohol Isoprenol Benzyl alcohol (BoilingPoint, ° C.) (82.6) (108) (131.2) (205.3) X = CrO₃ g 65 65 65 65 Y =organic solvent, g 40 48   57.3 70 Y/X molar ratio   1.0   1.0   1.0  1.0 Reflux temperature, ° C. 89 92 92 98 Cr(VI) oxide, wt %   30.4    0.0120    1.25     0.0120 (ppm) (304,000)    (120)  (12,500)   (120)  BET surface area, m²/g 159  324  184  198  Density, g/cc    0.48   0.57    0.52    0.60

The isobutyl alcohol example resulted in a chromium(VI) oxide content of120 ppm and a high BET surface area of 324 m²/g. The Benzyl alcoholexample resulted in a chromium(VI) oxide content of 120 ppm and aslightly lower BET surface area of 198 m²/g.

Example 8—Cr(VI) Reduction Using C4 Alcohols—Butyl Alcohol Isomers

The reactor system set-up and recipe of Example 4 were used herein. X gof chromic acid (CrO₃) and Y g of the various butyl alcohol isomers aredepicted in the table below.

The chromium(VI) oxide content, surface area and density valuesillustrated in the table were measured from dried chromium(VI) oxidepowder (i.e. powder that was not calcined).

TABLE 7 effect of butyl alcohol isomers on Cr(VI) levels Sample #6 #7 #1(from Example 1) #8 Butanol Isomer n-butyl Sec-butyl Isobutyl Tert-butyl(Boiling Point, ° C.) alcohol alcohol alcohol alcohol (117.4) (99) (108)(82.2) X = CrO₃ g 65 65 65 65 Y = Butanol, g 48 48 48 48 Y/X molar ratio  1.0   1.0   1.0   1.0 Reflux temperature, 93 86 92 93 ° C. Cr(VI)oxide, wt %    0.58   27.6     0.0120   89.2 (ppm) (5800)  (276,000)   (120)  (892,000)    BET surface area, 190  224  324  N/A m²/g Density,g/cc    0.51    0.52    0.57 N/A

Isobutyl alcohol outperformed the other butyl alcohol isomers withrespect to the resulting low chromium(VI) oxide content (120 ppm), highBET surface area (324 m²/g) and median density (0.57 g/cc). n-butylalcohol followed with a low chromium(VI) oxide content (5800 ppm),somewhat high BET surface area (190 m²/g) and median density (0.51g/cc).

Example 9—Cr(VI) Reduction Using Different Isobutyl Alcohol/CrO₃ MolarRatios

The reactor set-up and recipe of Example 4 were used herein. X g ofchromic acid (CrO₃) and Y g of isobutyl alcohol as depicted in the tablebelow. The chromium(VI) oxide content, surface area and density valuesillustrated in the table were measured from dried chromium(VI) oxidepowder (i.e. powder that was not calcined).

TABLE 8 isobutyl alcohol/CrO₃ molar ratio effect on Cr(VI) levels Sample#9 #10 #11 #12 X = CrO₃ g 55 55 55 55 Y = Isobutyl Alcohol, g 30 40 4562 Y/X molar ratio 0.74 0.98 1.1 1.51 Cr(VI) oxide, ppm 200 170 2,3105,000 BET surface area, m²/g 273 286 252 323 Density, g/cc 0.49 0.490.46 0.52

There is an optimal window of isobutyl alcohol/CrO₃ molar ratio thatwill result in the lowest CrO₃ content and highest BET surface area.

Example 10—Cr(VI) Oxide Reduction Using Organic Solvents Derived fromIsobutyl Alcohol Oxidation

The reactor set-up and recipe of Example 4 were used herein. X g ofchromic acid (CrO₃) and Y g of various organic solvents are depicted inthe table below. As illustrated in the table below, bothisobutyraldehyde and isobutyric acid may be used as an organic reducingsolvent for chromium(VI) oxide level reduction. The chromium(VI) oxidecontent, surface area and density values illustrated in the table weremeasured from dried chromium(VI) oxide powder (i.e. powder that was notcalcined).

TABLE 9 organic solvent effect on Cr(VI) oxide levels Sample #1 (fromExample 1) #13 #14 Organic Solvent Isobutyl Isobutyraldehyde Isobutyric(Boiling Point, ° C.) Alcohol (108) (63) acid (155) X = CrO₃ g 65 52 65Y = Organic Solvent, g 48 75 114.5 Y/X molar ratio 1.0 2.0 2.0 RefluxTemperature, ° C. 92 71 98 Cr(VI) oxide, ppm 120 12,120 9,040 BET, m²/g324 186 151 Density, g/cc 0.57 0.49 0.62

Example 11—Cr(VI) Oxide Reduction with Two Organic Reducing Solvents

The following reactor set-up and general recipe were used for Example 12below. Specific alterations will be detailed in the correspondingexample.

Reactor System Set-Up

A one liter 4-neck flask equipped with agitator, reflux condenser,coolant chiller, reactor heater, heater controller, temperature probeand recorder, dropping funnel, distillate receiver with ice bath, andnitrogen purge line, etc. was used for lab experiment runs.

Recipe

-   -   1) Charge 688 g of DI-H₂O into reactor;    -   2) Charge X g of chromic acid into reactor, mix for 5-10 minutes        with a fixed rate of agitation for a complete solid dissolution        with a uniform color;    -   3) Pump Y g of first organic chemical within 20 to 120 minutes        under constant agitation;    -   4) Pump Z g of second organic chemical within 30 minutes under        constant agitation either before reactor hear-up or post reflux        cycle;    -   5) Heat the mixture inside reactor to a reflux point of a binary        or ternary azeotropic phase;    -   6) Keep refluxing within the reactor system for a cycle time of        12-16 hours;    -   7) Strip off 400-415 g of a mixture of organic chemicals and        water;    -   8) Unload the slurry into a dryer for overnight drying at        120-150° C.; and    -   9) Calcine the dried powder under nitrogen at 300-500° C.        overnight.

Example 12—Cr(VI) Oxide Reduction Using Two Organic Solvents

The reactor set-up and recipe of Example 11 were used herein. X g ofchromium(VI) oxide (CrO₃), Y g of ethanol, and Z g of various carboxylicacids are depicted in the table below. As illustrated in Table 10,adding carboxylic acids, such as acetic acid and isobutyric acid,successfully reduces the level of chromium(VI) oxide. For example, in asystem of multiple organic solvents combining ethanol and isobutyricacid (#16), both the dried powder and the calcined powder intermediatesillustrated a chromium(VI) oxide level (210 ppm). A multiple organicsolvent system combining ethanol and acetic acid (#15) also generates acalcined catalyst powder with chromium(VI) oxide levels well below theregulatory limits (90 ppm). However, since the intermediate dried powderhas higher content of chromium(VI) oxide, a close powder transfer systemcould be required for handling the Cr₂O₃ catalyst produced by theprocess of sample #15.

TABLE 10 multiple organic solvents effect on Cr(VI) oxide levels Sample#15 #16 X = CrO₃ g 55 65 Y = Ethanol, g 38 45 Y/X molar ratio   1.5  1.5 Z = Carboxylic Acid, g Acetic Acid - 15 g Isobutyric acid - Chargeethanol first 46.6 g Charge post- then acetic acid ethanol reflux cyclebefore reactor with an additional heat-up 1 hour reflux after additionZ/X molar ratio    0.45    0.81 Reflux Temperature, ° C. 90 (ternary92-binary azeotropic) azeotropic 94-ternary azeotropic Dried Cr(VI)oxide,   10.2    0.021 Powder wt % (ppm) (102,000)    (210)  BET surfacearea, 242  247  m²/g Calcined Cr(VI) oxide,    0.009    0.021 Powder wt% (ppm) (90) (210)  BET surface area, 265  268  m²/g

The use of the terms “a,” “an,” “the,” and similar referents in thecontext of describing the materials and methods discussed herein(especially in the context of the following claims) are to be construedto cover both the singular and the plural, unless otherwise indicatedherein or clearly contradicted by context. Recitation of ranges ofvalues herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate the materials and methods and does not pose a limitation onthe scope unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the disclosed materials and methods.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “some embodiments,” “one or more embodiments” or “anembodiment” means that a particular feature, structure, material, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present disclosure. Thus, theappearances of the phrases such as “in one or more embodiments,” “incertain embodiments,” “in some embodiments,” “in one embodiment,” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the present disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreimplementations.

Although the embodiments disclosed herein have been described withreference to particular embodiments, it is to be understood that theseembodiments are merely illustrative of the principles and applicationsof the present disclosure. It will be apparent to those skilled in theart that various modifications and variations can be made to the methodand apparatus of the present disclosure without departing from thespirit and scope of the disclosure. Thus, it is intended that thepresent disclosure include modifications and variations that are withinthe scope of the appended claims and their equivalents, and theabove-described embodiments are presented for purposes of illustrationand not of limitation.

In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

1-85. (canceled)
 86. A chromium oxide catalyst composition comprising: achromium(III) oxide; and a chromium(VI) oxide present at an amount ofabout 10,000 ppm or less based on total chromium oxides content in thechromium oxide catalyst composition, wherein the chromium oxide catalystcomposition has a BET surface area of about 150 m²/g or more, andwherein the chromium(III) oxide and the chromium(VI) oxide, in total,are present at an amount of about 96 wt % or more based on total weightof the chromium oxide catalyst composition.
 87. The chromium oxidecatalyst composition of claim 86, wherein the chromium(VI) oxide ispresent at an amount of about 5,000 ppm or less based on total chromiumoxides content in the chromium oxide catalyst composition.
 88. Thechromium oxide catalyst composition of claim 86, wherein thechromium(III) oxide is present in an amount of about 99 wt % or morebased on total chromium oxides content in the chromium oxide catalystcomposition.
 89. The chromium oxide catalyst composition of claim 86,wherein the chromium oxide catalyst composition is a xerogel, andwherein the xerogel is about 80% or more amorphous.
 90. The chromiumoxide catalyst composition of claim 86, wherein the chromium oxidecatalyst composition is in a form of pellets, beads, extrudates, rings,spheres, cylinders, trilobe, or quadralobe shaped pieces.
 91. Thechromium oxide catalyst composition of claim 86, wherein the chromiumoxide catalyst composition is in contact with a substrate.
 92. Thechromium oxide catalyst composition of claim 86, wherein the substratecomprises alumina (Al₂O₃), aluminum fluoride (AlF₃), fluorinatedalumina, silica (SiO₂), titania (TiO2), zirconia (ZrO₂), magnesium oxide(MgO), magnesium fluoride (MgF₂), calcium fluoride (CaF₂), carbonmaterials (such as activated carbon, charcoal, or carbon black), orcombinations thereof.
 93. A process for preparing a chromium oxidecatalyst composition, the process comprising: forming a mixturecomprising chromium(VI) oxide in an aqueous solvent and in an organicreducing solvent; refluxing the mixture to form a slurry; and drying theslurry to form a powder having chromium(VI) oxide at an amount of about10,000 ppm or less based on total chromium oxides content in the powder.94. The process of claim 93, wherein the process further comprisesreducing the chromium(VI) to a chromium(III).
 95. The process of claim93, wherein the process further comprises oxidizing the organic reducingsolvent.
 96. The process of claim 93, wherein the organic reducingsolvent comprises isobutyl alcohol, and wherein the process furthercomprises: oxidizing the isobutyl alcohol to form isobutyraldehyde andisobutyric acid; and reacting the isobutyric acid with the chromium(VI)oxide in the aqueous solvent to form acetone and carbon dioxide.
 97. Theprocess of any one of claim 93, wherein the refluxing is performed at atemperature ranging from about 50° C. to about 250° C.
 98. The processof claim 93, wherein the dried powder is a xerogel.
 99. The process ofclaim 98, wherein the xerogel is about 80% or more amorphous.
 100. Theprocess of claim 93, wherein the dried powder contains chromium(VI)oxide at an amount of about 5,000 ppm or less based on total chromiumoxides content present in the powder.
 101. The process of claim 93,further comprising calcining the dried powder at a temperature rangingfrom about 300° C. to about 500° C.
 102. The process of claim 101,wherein the calcined dried powder contains chromium(VI) oxide at anamount of about 10,000 ppm or less based on total chromium oxidescontent present in the calcined dried powder.
 103. The process of claim93, further comprising blending the dried powder with a lubricant. 104.The process of claim 93, wherein the molar ratio of the organic reducingsolvent to the chromium(VI) oxide ranges from about 0.2 to about 4.0.105. A chromium oxide catalyst system comprising: a substrate; achromium oxide catalyst composition in contact with the substrate, thechromium oxide catalyst composition comprising: a chromium(III) oxide;and a chromium(VI) oxide present at an amount of about 10,000 ppm orless based on total chromium oxides content in the chromium oxidecatalyst composition, wherein the chromium oxide catalyst compositionhas a BET surface area of about 150 m²/g or more, and wherein thechromium(III) oxide and the chromium(VI) oxide, in total, are present atan amount of about 96 wt % or more based on total weight of the chromiumoxide catalyst composition.